Crosman Town & Country 107

[jirushi]

Pfew, I am getting there. 5,5 ft/lbs with 8 pumps.

@45flint, pumping the gun up and leaving overnight was a good idea. It had lost all pressure this morning.

I had to dis- and reassemble the gun a couple of times to solve a few issues.

One was the brass part holding the pump cup in place - it is now all the way down. The pump cup edge still doesn't protrude though; the alu base of the pump head and the brass part around it stick out a tiny little bit. I'm not sure whether this is normal or not. I compared the "height" of the new pump cup with the old one: it's the same. But maybe the original cup was higher?

Then the exhaust body gasket. It wasn't on the exhaust body anymore. The groove in the exhaust body to hold the gasket is quite shallow. And the gasket isn't tight like an o-ring. The fact that it wasn't in place, explains why the rifle lost pressure overnight.

Then the check valve spring. I'm not sure yet which works best: the short one that was in the gun, or the longer, new one in Rick's seal kit.
I think the latter. It's in the gun now. The weaker spring might not shut the check valve well enough? Or is the stronger check valve spring causing the check valve to be too difficult to open for the air to flow into the valve chamber...? But then the air pressure inside the valve chamber is probably stronger than the spring. Will have to test.

5,5 ft/lbs is not that fantastic, but it's something. It's 550 ft/s with 8.44 gr JSB's.
I also cleaned the barrel - that wasn't a bad idea!

I hope to get to about 8 ft/lbs, maybe I need to work on the bolt. Ped you wrote about lapping the bolt. I will need to find out what this means. Is it adding lead on the bolt head, in order to improve its fit in the barrel? Another option would be to make a groove on the bolt, for it to accept and o-ring? This would be a bad idea on the originality front though...

An o-ring pump head would be a great idea, to test the difference. The problem might still be the cup not sealing well enough.
A hint towards this theory is that pumping becomes harder up to 8 or 9 pumps, but then it's not that much more difficult to go 12 pumps, and the velocity increase is marginal. Maybe the pump is then simply not coping with the pressure, and leaking air - without me hearing it.



The two different check valve springs



And lastly, Christmas is coming...